Epidemiologic clinical and laboratory aspects of how infections develop in drug abusers will continue over the next year. Because Staphylococcus aureus is the single most important cause of infections in parenteral drug abusers, we are expanding our knowledge in the area of diagnosing serious staphylococcal infections in these patients. Basic mechanisms of the development of antibodies to teichoic acids in the cell walls of staphylococci will continue. The kinetics of antibody formation and the immunoglobulin types of antibodies formed during the development of a response will be elucidated. The use of counterimmunoelectrophoresis to screen for seriously ill patients with staphylococcal infections in emergency rooms servicing large numbers of drug abusers will be explored. Laboratory studies of how injected drugs predisposed to endocarditis will be initiated. The effect of narcotics on bacterial growth and on in vivo and in vitro host defense mechanisms in experimental animals will be clarified. Finally, the effect of narcotics and other injected drugs on the susceptibility of experimental animals to bacterial, fungal, and parasitic infections will be undertaken. BIBLIOGRAPHIC REFERENCES: Nagel JC, Tuazon CU, Cardella TA, Sheagren JN: Teichoic acid serologic diagnosis of staphylococcal infection: use of gel diffusion and counterimmunoelectrophoretic methods. Ann Intern Med 82:13-17, Jan 1975. Tuazon CU, Sheagren JN: Teichoic acid antibodies in the diagnosis of serious infections with Staphylococcus aureus. Ann Intern Med 84:543-546, May 1976.